Method of checking the functioning of a driving wheel slip control system

ABSTRACT

A method of checking the functioning of a driving wheel slip control system installed in a vehicle. Driving wheels are placed on support rollers and rotatably supported thereby. The driving wheels are driven by the engine. False signals indicative of tentative rotational speeds of trailing wheels are supplied to an ECU which in turn outputs a control signal for controlling the engine. Predetermined monitoring signals including at least the control signal output from the ECU are taken out from the driving wheel slip control system. It is determined whether the predetermined monitoring signals show values falling within respective predetermined allowable ranges. Further, a steering handle of the vehicle may be turned at the same time of rotation of the driving wheels, the steering angle of which is detected by a steering angle sensor. Further, instead of using the false signals, the trailing wheels may be placed on second support rollers for rotatably supporting the trailing wheels thereby. The second support rollers are capable of rotatively driving the trailing wheels.

BACKGROUND OF THE INVENTION

This invention relates to a method of checking the functioning of acontrol system installed in an automotive vehicle, and more particularlyto a method of checking the functioning of a driving wheel slip controlsystem.

As recognized in general, a driving wheel of an automotive vehicleundergoes a slip when the vehicle is started to run or when it isaccelerated, if the driving force of the driving wheel surpasses africtional force developed between the tire of the driving wheel and theroad surface [=the coefficient of friction between the tire and the roadsurface×load of the vehicle weight on the driving wheel (wheel load)].

Driving wheel slip control systems for controlling slips of drivingwheels have already been proposed by the present assignee, e.g. inJapanese Provisional Patent Publications (Kokai) Nos. 2-157439 and2-157440. According to these systems, driving wheel slip control iscarried out by the following steps:

1) detecting the rotational speeds of right and left driving wheels, therotational speeds of right and left trailing wheels, and the steeringangle of a steering handle,

2) calculating a parameter (hereinafter referred to as "the slip value")indicative of the degree of a slip of the driving wheels based on thedetected rotational speeds of the wheels and steering angle, and

3) increasing the number of cylinders of an internal combustioninstalled in the vehicle to be subjected to fuel cut to thereby decreasethe output torque of the engine as the slip value is larger (the degreeof the slip is larger).

The detection of the steering angle carried out at the above step 1) isfor controlling the yawing motion of the vehicle based on the detectedvalues of the steering angle and rotational speeds of the right and lefttrailing wheels. This control of the yawing motion is carried out bydecreasing the output torque of the engine, e.g., for the purpose ofreducing the tendency of the front-wheel-drive vehicle during yawingthereof toward understeering. The yawing motion control is a kind ofdriving wheel slip control in a broad sense.

On the other hand, a system for checking functioning or operation ofsuch driving wheel slip control systems has already been proposed byJapanese Provisional Utility Model Publication (Kokai) No. 63-84544, inwhich all the four wheels of a vehicle are placed on respective drumrollers capable of rotation independently of one another (these drumrollers, the equivalent inertial weights of which are small, play therole as a frozen road or the like), and it is determined that thedriving wheel slip control system of the vehicle is not normallyfunctioning if the rotational speeds of the right and left drivingwheels exceed a predetermined upper limit value within a predeterminedtime period after the accelerator pedal of the vehicle is stepped on.

According to the above proposed system, the checking is so roughlycarried out that it is only possible to determine whether the drivingwheel slip control system has operated or not. However, it is notpossible to determine whether driving wheel slip control systems likethe aforementioned ones proposed by the present assignee which arecapable of sensitive control are properly functioning to perform variouskinds of control as designed. More specifically, the above proposedchecking system cannot determine e.g. whether the slip value is properlycalculated based on the rotational speeds of the right and left drivingwheels, those of the right and left trailing wheels, and the steeringangle of the steering handle, and whether fuel cut and/or other controlare properly carried out based on the calculated slip value.

Further, since the conventional checking system uses data based solelyon the rotational speeds of the wheels, it is impossible to determinewhich part of the control system is faulty when it is determined to beout of order.

SUMMARY OF THE INVENTION

It is the object of the invention to provide a method of checking thefunctioning of a driving wheel slip control system, which is capable ofpositively determining whether the driving wheel control system which iscapable of complicated and sensitive control is properly functioning asdesigned.

A further object of the invention is to easily locate the faulty part ofthe control system when it is determined to be out of order.

To attain the above objects, according to a first aspect of theinvention, there is provided a method of checking the functioning of adriving wheel slip control system which is installed in a vehicle havingdriving wheels and trailing wheels, the driving wheel slip controlsystem having a prime mover (i.e. engine) for driving the drivingwheels, at least one driving wheel speed sensor for detecting therotational speed of at least one of the driving wheels and generating atleast one signal indicative of the rotational speed of the at least onedriving wheel, at least one trailing wheel speed sensor for detectingthe rotational speed of at least one of the trailing wheels andgenerating at least one signal indicative of the rotational speed of theat least one trailing wheel, and a control device responsive to thesignals indicative of the rotational speeds of the at least one drivingwheel and the at least one trailing wheel for outputting a controlsignal for controlling the output of the engine.

The method according to the first aspect of the invention ischaracterized by comprising the steps of:

(1) placing the driving wheels on a support device for rotatablysupporting the driving wheels by the support device;

(2) causing the engine to rotatively drive the driving wheels;

(3) supplying at least one false signal indicative of the rotationalspeed of the at least one trailing wheel to the control device in placeof the at least one signal indicative of the rotational speed of the atleast one trailing wheel;

(4) taking out predetermined monitoring signals including at least thecontrol signal output from the control device, from the driving wheelslip control system; and

(5) determining whether the predetermined monitoring signals show valuesfalling within respective predetermined allowable ranges.

According to a second aspect of the invention, the method ischaracterized by comprising the steps of:

(1) placing the driving wheels on a first support device for rotatablysupporting the driving wheels by the first support device;

(2) placing the trailing wheels on a second support device for rotatablysupporting the trailing wheels by the second support device, the secondsupport device being capable of rotatively driving the trailing wheels;

(3) causing the engine to rotatively drive the driving wheels;

(4) causing the second support device to rotatively drive the trailingwheels;

(5) taking out predetermined monitoring signals including at least thecontrol signal output from the control device, from the driving wheelslip control system; and

(6) determining whether the predetermined monitoring signals show valuesfalling within respective predetermined allowable ranges.

According to a third aspect of the invention, there is provided a methodof checking the functioning of a driving wheel slip control system whichis installed in a vehicle having driving wheels, trailing wheels, and asteering handle, the driving wheel slip control system having an enginefor driving the driving wheels, at least one driving wheel speed sensorfor detecting the rotational speed of at least one of the driving wheelsand generating at least one signal indicative of the rotational speed ofthe at least one driving wheel, at least one trailing wheel speed sensorfor detecting the rotational speed of at least one of the trailingwheels and generating at least one signal indicative of the rotationalspeed of the at least one trailing wheel, a steering angle sensor fordetecting a steering angle of the steering handle and generating asignal indicative of the steering angle, and a control device responsiveto the signals indicative of the rotational speeds of the at least onedriving wheel and the at least one trailing wheel and the steering anglefor outputting a control signal for controlling the output of theengine.

The method according to the third aspect of the invention ischaracterized by comprising the steps of:

(1) placing the driving wheels on a support device for rotatablysupporting the driving wheels by the support device;

(2) causing the engine to rotatively drive the driving wheels;

(3) supplying at least one false signal indicative of the rotationalspeed of the at least one trailing wheel to the control device in placeof the at least one signal indicative of the rotational speed of the atleast one trailing wheel;

(4) turning the steering handle;

(5) taking out predetermined monitoring signals including at least thecontrol signal output from the control device, from the driving wheelslip control system; and

(6) determining whether the predetermined monitoring signals show valuesfalling within respective predetermined allowable ranges.

According to a fourth aspect of the invention, the method ischaracterized by comprising the steps of:

(1) placing the driving wheels on a first support device for rotatablysupporting the driving wheels by the first support device;

(2) placing the trailing wheels on a second support device for rotatablysupporting the trailing wheels by the second support device, the secondsupport device being capable of rotatively driving the trailing wheels;

(3) causing the engine to rotatively drive the driving wheels;

(4) causing the second support device to rotatively drive the trailingwheels;

(5) turning the steering handle;

(6) taking out predetermined monitoring signals including at least thecontrol signal output from the control device, from the driving wheelslip control system; and

(7) determining whether the predetermined monitoring signals show valuesfalling within respective predetermined allowable ranges.

Preferably, the predetermined monitoring signals include the at leastone signal indicative of the rotational speed of the at least onetrailing wheel.

Also preferably, the predetermined monitoring signals include the signalindicative of the steering angle.

Preferably, the predetermined monitoring signals include the at leastone signal indicative of the rotational speed of the at least onedriving wheel.

Also preferably, the predetermined monitoring signals include at leastone signal indicative of operating conditions of the engine.

The above and other objects, features, and advantages of the inventionwill become more apparent from the ensuing detailed description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the whole arrangement of a vehicleinspecting system to which is applied a method according to a firstembodiment of the invention, and related parts of a vehicle underinspection;

FIG. 2 is a view showing a manner of fixing the vehicle underinspection;

FIG. 3 is a partially-exploded perspective view of a support rollerarrangement;

FIG. 4 is an exploded perspective view showing the internal constructionof the support roller;

FIG. 5 is a schematic diagram showing the whole arrangement of theengine and driving wheel slip control system of the vehicle underinspection;

FIG. 6 is a diagram showing operating regions of the engine defined bythe intake pipe absolute pressure (P_(BA)) and the engine rotationalspeed (Ne);

FIG. 7 is a diagram showing a table showing the relationship between aslip value DUTY and traction control levels (LVL N-LVL 6);

FIG. 8 is a diagram showing a table for determining a cylinder orcylinders for which leaning of the air-fuel mixture or fuel cut is to beeffected in accordance with the traction control level;

FIG. 9 is a graph showing, by way of example, correction of ignitiontiming when leaning of the air-fuel ratio is carried out;

FIG. 10 is a view showing a variation of the support rollers; and

FIG. 11 is a block diagram of the whole arrangement of a vehicleinspecting system to which is applied a method according to a secondembodiment of the invention, and related parts of a vehicle underinspection.

DETAILED DESCRIPTION

The invention will be described in detail below with reference to thedrawings.

FIG. 1 shows the whole arrangement of a vehicle inspecting system towhich is applied a method according to a first embodiment of theinvention, and related parts of a vehicle under inspection. The vehicleunder inspection is a front-wheel-drive vehicle of which right and leftfront wheels 2_(FR), 2_(FL) are driven by an engine (prime mover) 5. Thevehicle is equipped with an automatic transmission 4. Driving wheelspeed sensors 9_(FR), 9_(FL) are provided for the respective right andleft driving wheels 2_(FR), 2_(FL), while trailing wheel speed sensors9_(RR), 9_(RL) are provided for respective right and left trailing(rear) wheels 2_(RR), 2_(RL). The driving and trailing wheel speedsensors detect the rotational speeds of the respective wheels, andsupply signals indicative of the detected rotational speeds of thewheels to an electronic control unit (hereinafter referred to as "theTCS-ECU") 8 for detecting slips of the driving wheels. Also connected tothe TCS-ECU 8 is a steering angle sensor 10 for detecting the steeringangle of a steering handle 3, and supplying a signal indicative of thedetected steering angle to the TCS-ECU 8. The steering angle sensor 10generates a signal indicative of an absolute angle of steering such thatthe rightward steering angle is represented by a positive value(e.g.+1°, +2° . . . ) and the leftward steering angle by a negativevalue (e.g -1°, -2° . . . ), with the neutral position of the steeringhandle represented by zero degree.

The vehicle 1 further includes an electronic control unit (hereinafterreferred to as "the ENG-ECU") 7 for controlling the operation of theengine 5 by fuel supply control and ignition timing control, and anelectronic control unit (hereinafter referred to as "the EAT-ECU") 6 forcontrolling the operation of the automatic transmission 4 by gearselection control, lock-up control, etc. The ENG-ECU 7, the EAT-ECU 6,and the TCS-ECU 8 are connected to each other. The ECU's 6 to 8 alsohave signal output terminals provided for use in checking of thefunctioning described in detail hereinafter.

FIG. 5 shows an example of arrangement of parts of the vehicle 1 whichfunctions as the driving wheel slip control system, and whereincomponent elements and parts corresponding to those shown in FIG. 1 areindicated by the same reference numerals as in FIG. 1.

Connected to the cylinder block of the engine 5 is an intake pipe 12across which is arranged a throttle body 13 accommodating a throttlevalve 13' therein. A throttle valve opening (θ_(TH)) sensor 14 isconnected to the throttle valve 13' for generating an electric signalindicative of the sensed throttle valve opening and supplying same tothe ENG-ECU 7.

Fuel injection valves 16, only one of which is shown, are inserted intothe intake pipe at locations intermediate between the cylinder block ofthe engine 5 and the throttle valve 13' and slightly upstream ofrespective intake valves, not shown. The fuel injection valves 16 areconnected to a fuel pump, not shown, and electrically connected to theENG-ECU 7 to have their valve opening periods controlled by signalstherefrom.

Ignition plugs 26 for respective cylinders, not shown, of the engine 5are electrically connected to the ENG-ECU 7 to have their ignitiontiming θ_(IG) controlled by signals therefrom.

An intake pipe absolute pressure (P_(BA)) sensor 18 is provided incommunication with the interior of the intake pipe 12 via a conduit 17at a location immediately downstream of the throttle valve 13' forsupplying an electric signal indicative of the sensed absolute pressurewithin the intake pipe 12 to the ENG-ECU 7. An intake air temperature(T_(A)) sensor 19 is inserted into the intake pipe 12 at a locationdownstream of the intake pipe absolute pressure sensor 18 for supplyingan electric signal indicative of the sensed intake air temperature T_(A)to the ENG-ECU 5.

An engine coolant temperature (T_(W)) sensor 20, which may be formed ofa thermistor or the like, is mounted in the cylinder block of the engine5, for supplying an electric signal indicative of the sensed enginecoolant temperature T_(W) to the ENG-ECU 7. An engine rotational speed(Ne) sensor 21 and a cylinder-discriminating (CYL) sensor 22 arearranged in facing relation to a camshaft, not shown, or a crankshaft,not shown, of the engine 5. The engine rotational speed sensor 21generates a pulse as a TDC signal pulse at each of predetermined crankangles whenever the crankshaft rotates through a predetermined angle.The cylinder-discriminating sensor 22 generates a pulse at apredetermined crank angle of a particular cylinder of the engine. Boththe pulses generated by the sensors 21 and 22 are supplied to theENG-ECU 5.

A three-way catalyst 24 is arranged within an exhaust pipe 23 connectedto the cylinder block of the engine 5 for purifying noxious componentssuch as HC, CO, and NOx. An O₂ sensor 25 as an exhaust gas ingredientconcentration sensor is mounted in the exhaust pipe 23 at a locationupstream of the three-way catalyst 24, for sensing the concentration ofoxygen present in exhaust gases emitted from the engine 5 and supplyingan electric signal indicative of the sensed oxygen concentration to theENG-ECU 7.

The ENG-ECU 7 comprises an input circuit 7a having the functions ofshaping the waveforms of input signals from various sensors and theTCS-ECU 8, shifting the voltage levels of sensor output signals to apredetermined level, converting analog signals from analog-outputsensors to digital signals, and so forth, a central processing unit(hereinafter referred to as "the CPU") 7b, memory means 7c storingvarious operational programs which are executed in the CPU 7b and forstoring results of calculations therefrom, etc., and an output circuit7d which outputs driving signals to the fuel injection valves 16 and theignition plugs 26.

The CPU 7b operates in response to the above-mentioned signals from thesensors to determine operating conditions in which the engine 5 isoperating, such as an air-fuel ratio feedback control region forcontrolling the air-fuel ratio in response to the output from the O₂sensor 25 to a stoichiometric aif-fuel ratio, and open-loop controlregions, and calculates, based upon the determined operating conditions,the valve opening period or fuel injection period T_(OUT) over which thefuel injection valves 16 are to be opened, by the use of the followingequation (1) in synchronism with inputting of TDC signal pulses to theENG-ECU 7.

    T.sub.OUT =Ti×K.sub.1 ×K.sub.TCS +K.sub.2      (1)

where Ti represents a basic fuel injection period of the fuel injectionvalves 16, which is determined based upon the engine rotational speed Neand the intake pipe absolute pressure P_(BA).

K_(TCS) represents a leaning coefficient which is set to a value smallerthan 1.0, as described in detail hereinafter, when an excessive slipstate of the driving wheels is detected, and set to 1.0 when noexcessive slip state is detected.

K₁ and K₂ represent correction coefficients and correction variables,respectively, which are calculated based on various engine operatingparameter signals to such values as to optimize operatingcharacteristics of the engine such as fuel consumption andaccelerability, depending on operating conditions of the engine.

The CPU 5b determines ignition timing θ_(IG) depending on the enginerotational speed Ne and the intake pipe absolute pressure P_(BA).

The CPU 5b supplies through the output circuit 7d driving signals fordriving the fuel injection valves 16 and the ignition plugs 26 basedupon the results of the above determinations and calculations.

The TCS-ECU 8 calculates a slip value DUTY as a parameter indicative ofa slip state of the driving wheels, based on detected driving wheelspeeds W_(FR), W_(FL) of the right and left driving wheels 2_(FR),2_(FL), trailing wheel speeds W_(RR), W_(RL) of the right and lefttrailing wheels 2_(RR), 2_(RL), and steering angle δ, in the followingmanner, and then supply the calculated slip value DUTY to the ENG-ECU 7:

(1) An average value (hereinafter simply referred to as "the drivingwheel speed") V_(W) of the driving wheel speeds W_(FR), W_(FL) iscalculated.

(2) An average value (hereinafter simply referred to as "the vehiclespeed") V_(V) of the trailing wheel speeds W_(RR), W_(RL) is calculated.

(3) A reference driving wheel speed Vref is calculated based on thevehicle speed V_(V). The reference driving wheel speed Vref iscalculated based on the relationship between the trailing wheel speedand the driving wheel speed, which holds in a state where there isalmost no slip of the driving wheels and at the same time the vehicle 1is running straight.

(4) A yaw rate (yawing speed of the vehicle 1) Y is calculated based ona difference ΔVr between the trailing wheel speeds WRR, WRL.

(5) A reference yaw rate (a yaw rate intended by the driver by turningthe steering handle) Yb is calculated based on the vehicle speed V_(V)and the steering angle δ.

(6) A correction term KB is calculated based on the yaw rate Y,reference yaw rate Yb, vehicle speed V_(V), and steering angle δ, andthe reference driving wheel speed Vref is corrected by the correctionterm KB.

(7) A slip value DUTY is calculated based on a corrected referencedriving wheel speed V'ref and the driving wheel speed V_(W). The slipvalue DUTY assumes a larger value as the degree of a slip of the drivingwheels is larger.

The thus calculated slip value DUTY basically represents a slip state ofthe driving wheels in the state where the steering handle is in theneutral position, i.e. the correction term KB=0, the slip state beingdetected based on the relationship between the driving wheel speed V_(W)and the reference driving wheel speed Vref. Further, the slip value DUTYobtained through correction of the reference driving wheel speed Vref bythe correction term KB represents a slip state of the vehicle 1 in thecase were the steering handle is being turned (the driver intends yawingthe vehicle 1). For example, let it be assumed that the steering handleis turned leftward by a certain angle δ₀, and the expected trailingwheel speeds W_(RR), W_(RL) of the right and left trailing wheels are 30km/h and 20 km/h. If both the detected trailing wheel speeds W_(RR),W_(RL) are 25 km/h, it means that the vehicle is running straightalthough the driver has turned the steering handle. Thus, it is detectedthat the vehicle 1 is in a slip or skidding state. If such a slip orskidding state of the vehicle 1 is detected, the correction term KB issubtracted from the reference driving wheel speed Vref, and thereforethe difference (V_(W) -V'ref) between the driving wheel speed V_(W) andthe corrected reference driving wheel speed V'ref (=Vref -KB) becomeslarger than the difference (V_(W) -Vref) between the driving wheel speedV_(W) and the reference driving wheel speed Vref, so that the slip valueDUTY assumes a larger value.

The above numerical values are mentioned by way of an example forexplanation purposes, and therefore it does not necessarily follow thatthe above described state actually occurs.

The ENG-ECU 7 carries out engine output control (hereinafter referred toas "reaction control") by fuel cut or leaning of the air-fuel mixturesupplied to the engine 5 based on the slip value DUTY. The tractioncontrol is carried out, e.g. in the following manner:

(1) Predetermined threshold values TCFCLVL 0 to TCFCLVL 6 are set foreach of predetermined engine operating regions (e.g. for each of zonesZONE 1 to ZONE 4 shown in FIG. 6) which are set in accordance with theengine rotational speed Ne and the intake pipe absolute pressure P_(BA).

(2) traction control levels (hereinafter simply referred to as "TClevels") LVL N to LVL 6 are determined, e.g. as shown in FIG. 7, inaccordance with the relationship between the slip value DUTY and thepredetermined threshold values TCFCLVL 0 to TCFCLVL 6. For example, whenthe slip value DUTY assumes a value between TCFCLVL 2 and TCFCLVL 3, theTC level is determined to be LVL 2. In addition, TCFCLVLMIN andTCFCLVLMAX in FIG. 7 represent the minimum and maximum values of theslip value DUTY, respectively.

(3) In accordance with the determined TC level, fuel cut or leaning ofthe mixture supplied to each cylinder is carried out, cylinder bycylinder, e.g. as shown in the table of FIG. 8. FIG. 8 is a controlpattern of fuel supply applied to a 6 cylinder-type engine. In thetable, symbol L and symbol F/C represent leaning of the mixture and fuelcut, respectively, and values 1 to 6 of the cylinder-correspondingnumber M designate a sequence of cylinders to be controlled. Forexample, in the case of the TC level being LVL 3, cylinderscorresponding respectively to M=1, 3, 5 are subjected to fuel cut, whilecylinders corresponding respectively to M=2, 4, 6 are subjected toleaning of the mixture. The leaning of the mixture is effected bysetting the correction coefficient K_(TCS) of the aforementionedequation (1) to a value smaller than 1.0.

(4) In concurrence with leaning of the mixture of the step (3), theignition timing is controlled, as shown in FIG. 9, in accordance withthe engine rotational speed Ne. More specifically, the ignition timingis advanced when the engine rotational speed Ne is in a range of 1,500tpm-2,000 rpm in order to prevent dielectric breakdown of the ignitionsystem, whereas the ignition timing is retarded when the enginerotational speed Ne is in a range of 2,000 rpm-7,000 rpm in order toprevent occurrence of knocking.

(5) The above traction control is inhibited when any of the enginerotational speed Ne, the engine coolant temperature T_(W), the intakeair temperature T_(A), the throttle valve opening θ_(TH), etc. is notwithin a respective predetermined range. Further, if the excessive slipstate of the driving wheels is dissipated by execution of the tractioncontrol, the fuel supply to each cylinder of the engine is notimmediately resumed, but is so controlled that the engine outputgradually increases.

Driving wheel slip control systems, like one described above, for avehicle equipped with ECU's similar to the TCS-ECU 8 and the ENG-ECU 7are disclosed in more detail in aforementioned Japanese ProvisionalPatent Publications (Kokai) Nos. 2-157439 and 2-157440 by the presentassignee.

Referring again to FIG. 1, the EAT-ECU 6 for controlling the automatictransmission 4 sends an ignition timing-retarding signal for retardingthe ignition timing θ_(IG) to the ENG-ECU 7 when the gear ratio of theautomatic transmission 4 is changed, in order to reduce a shockresulting from the change in the gear ratio. When the ignitiontiming-retarding signal by the EAT-ECU occurs concurrently with thesignal for retarding the ignition timing θ_(IG) by traction control, theignition timing θ_(IG) is controlled preferentially by the signal bytraction control.

The vehicle 1, under inspection, which has the above described functionsfor the driving wheel slip control is held in place by fixing means 46as shown in FIG. 2, in such a manner that the right and left drivingwheels 2_(FR), 2_(FL) are placed on a pair of rotatable support rollers30_(aR), 30_(bR) and a pair of rotatable support rollers 30_(aL),30_(bL), respectively.

FIG. 3 shows essential parts of a support roller arrangement includingthe support rollers 30_(a), 30_(b). A floating table 52 is arranged on apair of guide rails 51_(a), 51_(b) for sliding therealong in directionsindicated by the arrow Y. The guide rails 51_(a), 51_(b) are secured onan intermediate support member, not shown, which is arranged on guiderails, not shown, for sliding therealong, the guide rails extending indirections indicated by the arrow X (orthogonal to the directionsindicated by the arrow Y). Thus, the floating table 52 can move in bothdirections indicated by the arrows X and Y.

A rotary shaft 54 is fitted through the center of the floating table 52via a bearing 53. The rotary shaft 54 is inhibited from upward ordownward movement, but is rotatable via the bearing 53 relative to thefloating table 52. The upper end of the rotary shaft 54 is rigidlysecured to a support roller assembly 55 which has a generally U-shapedcross-section. The support roller assembly 55 has a bottom wall and apair of opposed side walls upwardly extending integrally from therespective ends of the bottom wall. The aforementioned pair of supportrollers 30_(a), 30_(b) are parallely rotatably supported between theopposed side walls and spaced from each other by a predetermineddistance. The support rollers 30_(a), 30_(b) are adapted to support acorresponding wheel 2 of the vehicle 1 under checking.

The suppor roller 30_(a) contains motor, and is driven for rotation bythe motor. Accordingly, the wheel 2 placed on the support rollers30_(a), 30_(b) is driven for rotation by its frictional contact with thesupport rollers 30_(a), 30_(b). FIG. 4 shows the interior constructionof the support roller 30_(a) containing the motor. The support roller30_(a) comprises a cylindrical casing 301, a coil 302 tightly fitted inand secured to the casing 301 by means of a support frame 304, and anarmature 303 arranged within the coil 302 in spaced relation thereto.The armature 303 arranged within the support roller 30_(a) is also shownin FIG. 2. In the case of this construction, the armature 303 is heldstationary, while the coil 302 and hence the cylindrical casing arerotatable.

Means for rotating the support roller may be provided separately fromthe support roller. Also, the support roller to be driven for rotationis not limited to 30_(a), but the support roller 30_(b) or both of thesupport rollers 30_(a), 30_(b) may be driven for rotation.

Referring again to FIG. 1, groups 31_(a), 31_(b) of sensors are mountedon the automatic transmission 4 and the engine 5 of the vehicle 1,respectively, for detecting respective operating parameters. The sensorgroup 31_(a) for the automatic transmission 4 includes an oil pressuresensor for detecting the pressure of operating oil, an oil temperaturesensor for detecting the temperature of operating oil. The sensor group31_(b) for the engine 5 includes, e.g. an engine rotational speedsensor, an intake pressure sensor, an engine coolant temperature sensor,an intake air temperature sensor, a sensor for detecting the temperatureof the catalyst of the exhaust gas purifying device (the three-waycatalyst 24), an engine oil temperature sensor, and air-fuel ratiosensors for detecting the air-fuel ratios of mixtures supplied to therespective cylinders. These sensors are attached to portions of theautomatic transmission 4 and the engine 5 which allow the sensors to beeasily mounted thereon or removed therefrom (e.g. the engine rotationalspeed sensor is attached to a wire for transmitting a signal for drivingthe ignition plug, and the engine oil temperature sensor to an oil levelgauge), or branched portions provided exclusively for sensors.

Signals from the sensor groups 31_(a), 31_(b) are supplied via apreamplifier 32 to an analyzing recorder 36.

Checking signal output terminals of the EAT-ECU 6, ENG-ECU 7, andTCS-ECU 8 are connected via monitors 33, 34, 35 to the analyzingrecorder 36. The EAT-ECU 6 supplies a control signal for controlling theautomatic transmission 4, to the analyzing recorder 36, the TCS-ECU 8supplies a signal indicative of the slip value DUTY to same, and theENG-ECU 7 supplies output signals from the various sensors (see FIG. 5)which detect operating conditions of the engine 5, and driving signalsfor the fuel injection valves 16 and ignition plugs 26 of the engine 5,to same.

The output signals from the ECU's 6 to 8 and sensor output signals maybe taken out from attachments connected to couplers of wire harnessesfor transferring these signals.

Wires electrically connecting the right and left driving wheel speedsensors 9_(FR), 9_(FL), and the steering angle sensor 10 of the steeringhandle 3 to the TCS-ECU 8, respectively, are bifurcated by respectiveattachments 43, 43 wherefrom signals from these sensors 9_(FR), 9_(FL),10 are supplied via a preamplifier 39 to a data recorder 40. The datarecorder 40 records the signals from the sensors 9_(FR), 9_(FL), 10, andsupplies data on the recorded signals to a computer 38, when required.

Also connected to the TCS-ECU 8 is a pulse generator 41 which suppliespulse signals to the TCS-ECU 8 as false signals for the signals from theright and left trailing wheel speed sensors 9_(RR), 9_(RL). Thus, therotational speeds of the right and left trailing wheels can be falsewiseset to any desired values by changing the frequencies of the pulsesignals from the pulse generator 41. Further, a motor-driving device 42is connected to the support rollers 30_(aR), 30_(aL) for exertingrunning resistance forces upon the driving wheels 2_(FR), 2_(FL) of thevehicle 1.

The monitor 35 and the analyzing recorder 36 both connected to theTCS-ECU 8 are equipped with data-storing devices (e.g. floppy diskdevices), for storing data on checking results in respective floppydisks 37. The data stored in the floppy disks 37 are analyzed by thecomputer 38, together with the data stored in the data recorder 40. Thedata-storing device of the monitor 35 is used when only the outputsignal from the TCS-ECU 8 is analyzed, and normally, analysis is carriedout based on the data stored by the analyzing recorder 36. Further, ifit is necessary to make data stored by the analyzing recorder 36synchronous with the data by the data recorder 40, one of thecorresponding signals inputted to the analyzing recorder 36 is alsoinput to the data recorder 40.

The checking system having the above described construction basicallycarries out 1) false realization of various running modes of the vehicle1 under checking, and 2) checking of operations of various parts of thevehicle related to the driving wheel slip control when the engine is ineach of the running modes.

The false realization of the running modes of the vehicle 1 is effected,e.g. in the following manner:

(1) The accelerator pedal is operated by the operator or an actuator tocause rotation of the driving wheels 2_(FR), 2_(FL), with the steeringangle δ of the steering handle 3 kept equal to 0 (which means that thevehicle is running straight).

(2) The false signals for the output signals from the trailing wheelspeed sensors are supplied to the TCS-ECU 8 from the pulse generator 41.

(3) Various slip states of the driving wheels are created by changingthe relationship between the driving wheel speeds W_(FR), W_(FL)obtained at the above step (1) and the frequencies of the false signalsindicative of the tentative trailing wheel speeds W_(RR), W_(RL)obtained at the step (2).

(4) Running resistance forces are exerted upon the driving wheels byactuating the motors contained in the support rollers 30_(aR), 30_(aL)to thereby create various slip states of the driving wheels asencountered when the vehicle 1 is running up a slope or when the vehicle1 is running down a slope, etc.

(5) The steering handle 3 is operated by the operator or the actuator tochange the steering angle, and at the same time the above steps (1) to(4) are carried out, to thereby realize various slip states of thevehicle 1 as encountered when it is turning.

Checking of the operations of parts of the vehicle 1 related to thedriving wheel slip control is carried out when the vehicle 1 is undereach of the running modes realized as above, by determining whether thechecking data input to the computer 38 as monitoring signals show valuesfalling within respective predetermined ranges allowable for the eachrunning mode of the vehicle. More specifically, the output signals fromEAT-ECU 6, ENG-ECU 7 and TCS-ECU 8, the signals from the sensor groups31_(a), 31_(b), and the signals from the right and left driving wheelspeed sensors 9_(FR), 9_(FL) and the steering angle sensor 10 are usedas the monitoring signals. Based upon these monitoring signals, checkingis carried out as to (1) whether each sensor is normally operating, (2)whether each ECU is normally operating, and (3) whether the automatictransmission 4 and the engine 5 are operating as instructed by thecontrol signals from the ECU's.

By checking the driving wheel slip control system installed in thevehicle 1 as described above, it is possible to determine, for each ofthe various running modes of the vehicle 1,

(1) whether the various sensors, particularly the right and left drivingwheel speed sensors 9_(FR), 9_(FL), and the steering angle sensor 10 arenormal,

(2) whether the value of the slip value DUTY is proper, which has beencalculated by the TCS-ECU 8 based on the detected rotational speedsW_(FR), W_(FL) of the respective right and left driving wheels, thedetected rotational speeds W_(RR), W_(RL) of the respective right andleft trailing wheels, and the detected steering angle δ,

(3) whether decision of leaning or fuel cut of the mixture to besupplied to each cylinder of the engine 5 based on the slip value DUTY(see FIG. 8), and decision of ignition timing, are properly carried outby the ENG-ECU 7 and

(4) whether the engine 5 is properly operating in response to thecontrol signals from the ENG-ECU 7.

Therefore, in cases where the driving wheel slip control system is notnormally functioning, it can be immediately determined whether this iscaused by a sensor, or by an ECU, or by the engine 5 (or a wireconnecting the engine 5 to an ECU).

Although in the above described embodiment, the support rollers 30_(a),30_(b) are so constructed that as shown in FIG. 3, they can be rotatedabout the rotary shaft 54 in unison therewith in horizontal directionsto realize a false running state of the vehicle 1 in which it is runningwhile turning. However, the function of rotating the support rollers inhorizontal directions may be omitted to realize a false running state ofthe vehicle in which it is only running straight. In such an alternativearrangement, a pair of right and left support rollers 30_(aR), 30_(aL)may be integrally formed in a single piece, and also another pair30_(bR), 30_(bL) in a single piece, as shown in FIG. 10.

FIG. 11 shows the whole arrangement of a vehicle checking system towhich is applied a method according to a second embodiment of theinvention.

In FIG. 11, corresponding elements and parts to those in FIG. 1 aredesignated by identical numerals, and detailed description of which isomitted. This embodiment is distinguished from the above described firstembodiment only in the following points:

In this embodiment, support rollers 44_(aR), 44_(bR), and 44_(aL),44_(bL) are provided for supporting trailing wheels 2_(RR), 2_(RL) ofthe vehicle 1, respectively. These support rollers 44a, 44b, and asupport roller arrangement including them are identical in constructionwith those shown in FIG. 3. A motor-driving device 45 is connected tothe support rollers 44_(aR), 44_(aL), for causing rotation of thetrailing wheels 2_(RR), 2_(RL) of the vehicle 1 at desired rotationalspeeds. Thus, the pulse generator 41 in the first embodiment is omitted.

Wires connecting trailing wheel speed sensors 9_(RR), 9_(RL) to theTCS-ECU 8 are bifurcated by an attachment 43 to supply signals fromthese sensors 9_(RR), 9_(RL) via the preamplifier 39 to the datarecorder 40.

In the first embodiment described before, the trailing wheels 2_(RR),2_(RL) are not actually rotated, but the pulse generator 41 is used togenerate false signals for the signals from the trailing wheel speedsensors 9_(RR), 9_(RL). However, in this embodiment, the trailing wheels2_(RR), 2_(RL) are also supported by the support rollers 44_(a), 44_(b),of which the support rollers 44_(aR), 44_(aL) containing respectivemotors actually drive the trailing wheels 2_(RR), 2_(RL), respectively.Therefore, the trailing wheel speeds W_(RR), W_(RL) are detected by therespective trailing wheel speed sensors 9_(RR), 9_(RL), and signalsindicative of the detected trailing wheel speeds W_(RR), W_(RL) aresupplied to the data recorder 40.

Except for the above described points, this embodiment is identical withthe first embodiment. Therefore, the same kinds of checking as in thefirst embodiment can be carried out. Further, operations of the trailingwheel speed sensors 9_(RR), 9_(RL) can be checked at the same time.

Also in this embodiment, checking of the driving wheel slip controlsystem with the vehicle running while turning may be omitted by omittingthe function of rotation of each support roller arrangement inhorizontal directions. Further, the right and left support rollers30_(a), 30_(b) supporting the front wheels and the right and leftsupport rollers 44_(a), 44_(b) supporting the rear wheels may be eachformed in a single piece in a manner similar to that shown in FIG. 10.

Further, although in the above embodiments, the support rollers 30_(a)contain the respective motors for exerting running resistance forcesupon the driving wheels, this is not limitative, but the support rollers30_(a) or 30_(b) may be provided with means for mechanically creatingresistance forces exerted upon the rollers 30_(a) or 30_(b) and hencebraking the driving wheels.

What is claimed is:
 1. A method of checking the functioning of a drivingwheel slip control system which is installed in a vehicle having drivingwheels and trailing wheels, said driving wheel slip control systemhaving a prime mover for driving said driving wheels, at least onedriving wheel speed sensor for detecting the rotational speed of atleast one of said driving wheels and generating at least one signalindicative of the rotational speed of said at least one driving wheel,at least one trailing wheel speed sensor for detecting the rotationalspeed of at least one of said trailing wheels and generating at leastone signal indicative of the rotational speed of said at least onetrailing wheel, and control means responsive to said signals indicativeof the rotational speeds of said at least one driving wheel and said atleast one trailing wheel for outputting a control signal for controllingthe output of said prime mover;the method comprising the steps of: (1)placing said driving wheels on support means for rotatably supportingsaid driving wheels by said support means; (2) causing said prime moverto rotatively drive said driving wheels; (3) supplying at least onefalse signal indicative of the rotational speed of said at least onetrailing wheel to said control means in place of said at least onesignal indicative of the rotational speed of said at least one trailingwheel: (4) taking out predetermined monitoring signals including atleast said control signal outputted from said control means, from saiddriving wheel slip control system; and (5) determining whether saidpredetermined monitoring signals show values falling within respectivepredetermined allowable ranges.
 2. A method of checking the functioningof a driving wheel slip control system which is installed in a vehiclehaving driving wheels, trailing wheels, and a steering handle, saiddriving wheel slip control system having a prime mover for driving saiddriving wheels, at least one driving wheel speed sensor for detectingthe rotational speed of at least one of said driving wheels andgenerating at least one signal indicative of the rotational speed ofsaid at least one driving wheel, at least one trailing wheel speedsensor for detecting the rotational speed of at least one of saidtrailing wheels and generating at least one signal indicative of therotational speed of said at least one trailing wheel, a steering anglesensor for detecting a steering angle of said steering handle andgenerating a signal indicative of said steering angle, and control meansresponsive to said signals indicative of the rotational speeds of saidat least one driving wheel and said at least one trailing wheel and saidsteering angle for outputting a control signal for controlling theoutput of said prime mover;the method comprising the steps of: (1)placing said driving wheels on support means for rotatably supportingsaid driving wheels by said support means; (2) causing said prime moverto rotatively drive said driving wheels; (3) supplying at least onefalse signal indicative of the rotational speed of said at least onetrailing wheel to said control means in place of said at least onesignal indicative of the rotational speed of said at least one trailingwheel; (4) turning said steering handle; (5) taking out predeterminedmonitoring signals including at least said control signal outputted fromsaid control means, from said driving wheel slip control system; and (6)determining whether said predetermined monitoring signals show valuesfalling within respective predetermined allowable ranges.
 3. A methodaccording to claim 2, wherein said predetermined monitoring signalsinclude said signal indicative of said steering angle.
 4. A methodaccording to any one of claims 1 or 2, wherein said predeterminedmonitoring signals include said at least one signal indicative of therotational speed of said at least one driving wheel.
 5. A methodaccording to any one of claims 1 or 2, wherein said predeterminedmonitoring signals include at least one signal indicative of operatingconditions of said prime mover.
 6. A method according to claim 2,wherein said predetermined monitoring signals include said at least onesignal indicative of the rotational speed of said at least one trailingwheel and said signal indicative of said steering angle.
 7. A methodaccording to claim 2, wherein said predetermined monitoring signalsinclude said signal indicative of said steering angle and at least onesignal indicative of operating conditions of said prime mover.
 8. Amethod according to claim 2, wherein said predetermined monitoringsignals include said at least one signal indicative of the rotationalspeed of said at least one trailing wheel, said signal indicative ofsaid steering angle, and at least one signal indicative of operatingconditions of said prime mover.